Systems and methods for defect material classification

Abstract

A inspection system includes an illumination source to generate an illumination beam, focusing elements to direct the illumination beam to a sample, a detector, collection elements configured to direct radiation emanating from the sample to the detector, a detection mode control device to image the sample in two or more detection modes such that the detector generates two or more collection signals based on the two or more detection modes, and a controller. Radiation emanating from the sample includes at least radiation specularly reflected by the sample and radiation scattered by the sample. The controller determines defect scattering characteristics associated with radiation scattered by defects on the sample based on the two or more collection signals. The controller also classifies the one or more particles according to a set of predetermined defect classifications based on the one or more defect scattering characteristics.

What is claimed: 
     
       1. A system, comprising:
 an illumination source configured to generate an illumination beam; 
 one or more focusing lenses configured to direct the illumination beam to a sample; 
 a detector; 
 one or more collection lenses configured to direct radiation emanating from the sample to the detector, wherein the radiation emanating from the sample includes radiation specularly reflected by the sample and radiation scattered by the sample; 
 one or more phase plates configured to introduce two or more different selected phase offsets between the radiation specularly reflected by the sample and the radiation scattered by the sample such that the detector generates two or more collection signals; and 
 a controller communicatively coupled to the detector, the controller including one or more processors configured to execute program instructions configured to direct the one or more processors to:
 determine one or more scattering phase values introduced to the illumination beam scattered by one or more defects on the sample based on the two or more collection signals; and 
 classify the one or more defects according to a set of predetermined defect classifications based on the one or more scattering phase values. 
 
 
     
     
       2. The system of  claim 1 , wherein the one or more phase plates comprise:
 two or more phase plates mounted on a translation stage communicatively coupled to the controller, wherein the translation stage is configured to sequentially insert the two or more phase plates into the radiation emanating from the sample to introduce the two or more selected phase offsets, wherein the two or more collection signals correspond to two or more signals sequentially generated by the detector in response to the radiation emanating from the sample modified by the two or more phase plates. 
 
     
     
       3. The system of  claim 1 , further comprising:
 one or more beamsplitters to separate the radiation emanating from the sample into two or more sample beams, wherein the one or more phase plates comprise: 
 two or more phase plates, wherein the two or more sample beams are directed to the two or more phase plates to introduce the two or more selected phase offsets, wherein the two or more collection signals correspond to two or more signals generated by two or more detector assemblies of the detector in response to the radiation emanating from the sample modified by the two or more phase plates. 
 
     
     
       4. The system of  claim 1 , wherein the one or more phase plates comprise:
 a translation stage to secure the sample, wherein the translation stage is communicatively coupled to the controller, wherein the translation stage is configured to translate the sample to two or more focal positions along an optical axis of the one or more focusing lenses to introduce the two or more different selected phase offsets, wherein the two or more collection signals correspond to two or more signals generated by the detector at the two or more focal positions. 
 
     
     
       5. The system of  claim 1 , further comprising:
 one or more apertures configured to sequentially create a bright-field image on the detector as a first collection signal of the two or more collection signals based on the radiation emanating from the sample and a dark-field image on the detector as a second collection signal of the two or more collection signals based on the radiation emanating from the sample. 
 
     
     
       6. The system of  claim 1 , wherein at least a first one of the two or more collection signals comprise:
 a dry image, wherein at least one of the two or more collection signals comprises: 
 a water immersion image. 
 
     
     
       7. The system of  claim 1 , further comprising:
 an attenuation plate configured to reduce the intensity of illumination specularly reflected by the sample relative to illumination scattered by the sample. 
 
     
     
       8. The system of  claim 1 , wherein the set of predetermined defect classifications comprises:
 at least one of metals, dielectrics, or organic materials. 
 
     
     
       9. The system of  claim 1 , wherein the set of predetermined defect classifications comprises:
 at least one of silver, aluminum, gold, copper, iron, molybdenum, tungsten, germanium, silicon, silicon nitrate, or silicon dioxide. 
 
     
     
       10. The system of  claim 1 , wherein the radiation emanating from the sample further includes fluorescent radiation, wherein the one or more processors are further configured to:
 determine one or more fluorescent intensity values associated with illumination generated by one or more defects on the sample based on the two or more collection signals; and 
 classify the one or more defects according to a set of predetermined defect classifications based on the one or more fluorescent intensity values. 
 
     
     
       11. The system of  claim 1 , wherein the illumination beam comprises:
 an annular illumination beam. 
 
     
     
       12. The system of  claim 11 , wherein the illumination beam comprises:
 a spatially incoherent illumination beam. 
 
     
     
       13. The system of  claim 11 , wherein the illumination source comprises:
 a narrowband illumination source. 
 
     
     
       14. The system of  claim 13 , wherein the illumination source comprises:
 a speckle-busted laser source. 
 
     
     
       15. The system of  claim 11 , wherein the illumination source comprises:
 a broadband illumination source. 
 
     
     
       16. The system of  claim 15 , wherein the broadband illumination source comprises:
 an incoherent lamp source. 
 
     
     
       17. The system of  claim 15 , wherein the broadband illumination source comprises:
 a tunable broadband illumination source. 
 
     
     
       18. The system of  claim 11 , wherein the illumination beam comprises:
 a spatially coherent illumination beam. 
 
     
     
       19. The system of  claim 18 , wherein the illumination beam comprises:
 a laser source. 
 
     
     
       20. The system of  claim 19 , wherein the laser source comprises:
 a tunable laser source. 
 
     
     
       21. The system of  claim 1 , wherein the system further includes a polarizer mask in a pupil plane of the one or more collection lenses configured to suppress illumination scattered by a surface of the sample with respect to illumination scattered by the one or more defects on the sample. 
     
     
       22. The system of  claim 21 , wherein the illumination beam comprises:
 a single collimated illumination beam. 
 
     
     
       23. The system of  claim 21 , wherein the detector comprises:
 a time delay and integration (TDI) detector. 
 
     
     
       24. The system of  claim 1 , wherein the one or more focusing lenses and the one or more collection lenses share at least one common lens. 
     
     
       25. The system of  claim 1 , wherein the one or more phase plates comprises:
 a variable phase plate mounted on a translation stage communicatively coupled to the controller, wherein the translation stage is configured to sequentially modify a position of the variable phase plate with respect to the radiation emanating from the sample to introduce the two or more selected phase offsets, wherein the two or more collection signals correspond to two or more signals sequentially generated by the detector in response to the radiation emanating from the sample modified by the variable phase plate. 
 
     
     
       26. A system, comprising:
 an illumination source configured to generate an illumination beam; 
 one or more focusing elements configured to direct the illumination beam to a sample; 
 a detector; 
 one or more collection elements configured to direct radiation emanating from the sample to the detector, wherein the radiation emanating from the sample includes radiation specularly reflected by the sample and radiation scattered by the sample; 
 a translation stage to secure the sample, wherein the translation stage is configured to translate the sample to two or more focal positions along an optical axis of the one or more focusing lenses to introduce two or more different selected phase offsets between the radiation specularly reflected by the sample and the radiation scattered by the sample such that the detector generates two or more collection signals at the two or more focal positions; and 
 a controller communicatively coupled to the detector and the translation stage, the controller including one or more processors configured to execute program instructions configured to direct the one or more processors to:
 determine one or more scattering phase values introduced to the illumination beam scattered by one or more defects on the sample based on the two or more collection signals; and 
 classify the one or more defects according to a set of predetermined defect classifications based on the one or more scattering phase values. 
 
 
     
     
       27. A system, comprising:
 an illumination source configured to generate an illumination beam; 
 one or more focusing lenses configured to direct the illumination beam to a sample; 
 a detector; 
 one or more collection lenses configured to direct radiation emanating from the sample to the detector, wherein the radiation emanating from the sample includes radiation specularly reflected by the sample and radiation scattered by the sample; 
 a detection mode control device configured to sequentially create a bright-field image on the detector based on the radiation emanating from the sample as a bright-field collection signal and a dark-field image on the detector based on the radiation emanating from the sample as a dark-field collection signal; and 
 a controller communicatively coupled to the detector, the controller including one or more processors configured to execute program instructions configured to direct the one or more processors to:
 compare the bright-field collection signal and the dark-field collection signal to detect one or more defects on the sample; 
 determine defect absorption values for the one or more defects based on signal strengths of the one or more defects in the bright-field collection signal; 
 determine scattering intensity values for the one or more defects based on signal strengths of the one or more defects in the dark-field collection signal; and 
 classify the one or more defects according to a set of predetermined defect classifications based on the defect absorption values and the scattering intensity values of the one or more defects. 
 
 
     
     
       28. A system, comprising:
 an illumination source configured to generate an illumination beam; 
 one or more focusing lenses configured to direct the illumination beam to a sample; 
 a detector; 
 one or more collection lenses configured to direct radiation emanating from the sample to the detector, wherein the radiation emanating from the sample includes radiation specularly reflected by the sample and radiation scattered by the sample; 
 a chamber configured to contain the sample and an immersion medium; and 
 a controller communicatively coupled to the detector, the controller including one or more processors configured to execute program instructions configured to direct the one or more processors to:
 receive a dry collection signal from the detector generated with the immersion medium including a gas; 
 receive an immersion collection signal from the detector generated with the immersion medium including a liquid; 
 compare the dry collection signal and the immersion collection signal to detect one or more defects on the sample; and 
 classify the one or more defects according to a set of predetermined defect classifications based on the comparison of the dry collection signal and the immersion collection signal. 
 
 
     
     
       29. A method for defect classification, comprising:
 illuminating a sample with an illumination beam; 
 collecting illumination emanating from the sample using two or more detection modes, wherein the radiation emanating from the sample includes radiation specularly reflected from the sample and radiation scattered from the sample; 
 introducing two or more different selected phase offsets between the radiation specularly reflected by the sample and the radiation scattered by the sample to generate two or more collection signals; 
 determining one or more defect scattering phase values introduced to the illumination beam scattered by one or more defects on the sample based on the two or more collection signals; and 
 classifying the one or more defects according to a selected set of predetermined defect classifications based on the one or more scattering phase values.